1. Field of the Invention
The present application relates to an aspiration tube for a medical aspiration system.
2. Prior Art
The lens of a human eye may develop a cataracteous condition which affects a patients vision. Cataracteous lenses are sometimes removed and replaced in a procedure commonly referred to as phacoemulsification. Phaco procedures are typically performed with an ultrasonically driven handpiece which is used to break the lens. The broken lens is removed through an aspiration line that is coupled to the handpiece.
The handpiece has a tip which is inserted through an incision in the cornea. The handpiece typically contains a number of ultrasonic transducers that convert electrical power into a mechanical oscillating movement of the tip. The distal end of the tip has an opening that is in fluid communication with the aspiration line. The distal end of the tip also has a sleeve which has an opening in fluid communication with an irrigation line. The irrigation line is typically connected to a bottle that can provide irrigation fluid to the surgical site.
The oscillating movement of the tip breaks the lens into small pieces. The lens pieces and irrigation fluid are drawn into the aspiration line through the opening of the tip. When performing a phaco procedure it is essential to maintain a positive pressure within the anterior chamber of the eye. A negative pressure may cause the cornea to collapse. To maintain a positive chamber pressure the system is configured to provide a flow rate through the irrigation tube that is greater than the flow rate through the aspiration tube.
It has been found that the aspiration tube may become occluded during a procedure. The occlusion will increase the vacuum pressure within the aspiration line. When the occlusion is cleared the anterior chamber may be instantaneous exposed to a high vacuum pressure. The vacuum pressure may cause the cornea to collapse.
U.S. Pat. No. 6,478,781 issued to Urich et al. discloses a coiled tube that can be used to minimize pressure surges in an aspiration system. The tube has a length of at least 8 feet and a number of coils that create a fluidic resistance which minimizes vacuum surges. The recited inner diameter of the tube ranged from 0.06 to 0.1 inches, which is industry standard. Although effective, the coiled approach can only account for a limited pressure drop.
U.S. Pat. No. 6,599,271 issued to Easley and assigned to Syntec, Inc. discloses an aspiration system that has a flow restrictor and an in-line filter. Although flow restrictors can minimize vacuum surges, restrictors can create turbulent flow within the aspiration tube. Such turbulent flow can create air bubbles in the tube. When an occlusion occurs the air bubbles can collect and expand the tube. This may lead to an undesirable vacuum surge within the system.
It would be desirable to provide an aspiration system that minimizes the effects of a cleared occlusion within an aspiration tube of the system without having to use a flow restrictor, or coiled tubing.